The Odds of Four
by ecb327
Summary: AU, OOC, Star Trek/Sherlock crossover fic. Khan and Sherlock are twin brothers; Khan is the 'good one,' invested in his research with time travel, whereas Sherlock, bored out of his mind, uses less productive outlets to deal with pent-up brain power. Things change, however, when they run into another pair of partners in crime, and before they know it their two has become four. What
1. Chapter 1

_Author's note – _Alright, I need to stop writing fanfiction. But I can't. I'm a writing addict. I hope you guys enjoy it. Anyway. This one is a little different, given that it's a crossover. My lovely friend Leila (ephe-merely on tumblr, FYI) and I were talking about how we both want Benedict Cumberbatch (who doesn't?) and she suggested we split him in 2, and I suggested that she gets Sherlock and I get Khan, and then this fic kind of happened. The characters of Leila and Edye are really extremely true to ourselves, which has been so fun doing. Anyway. I really hope you like this, so please review/follow/favorite to let me know that you'd like me to continue.

—

He was leaning languidly against the side of _Coffee Beans & Co. _when they met.

"Happy Valentine's day," she said, rather sardonically.

"Mm," he said, absently wondering why she was talking to him.

"How's business?"

"Dull. That's to be expected. The oxytocin release is exceptionally nauseating today. The appeal of intentionally temporary social interactions - dating, I believe, is the ubiquitous term - is something I will likely never understand."

"I agree. Want one?" She passed him a cigarette and lit it up. They stood in surprisingly comfortable silence, given that they were strangers and it was not a habit of Sherlock's to engage in mundane conversations with random girls. This one was striking, though. Defined cheekbones, raven black hair, penetrating dark eyes.

"Sherlock," he said, a cursory introduction.

She nodded acknowledgement, saying nothing.

"And you are..?" Sherlock prompted her. The irony of him giving social cues was laughable.

"Oh. Leila."

"Right." There was no "nice to meet you," and he liked it that way.

Mrs. Hudson, his boss, poked her head out the side door and warned, "Five minutes. And put that damn thing out, it'll be the death of you."

He rolled his eyes. "As long as it doesn't impact my mental functionality, I'm good."

Leila continued to smoke unabashedly, and he couldn't help but note her full lips as double helices of vapor twined in the cold February air. "My best friend's like that," she empathized. "Anti-drinking, always telling me to be safe and careful and this, that, and the other." She rolled her eyes. "Caution is not really my area."

"Me neither," said Sherlock.

"Cool."

Five minutes passed. He found he was disappointed to leave her. "I'll see you around?"

"Maybe," she said, and stamped out the butt of her cigarette.

—

Khan was struggling. Sherlock had texted him several times, something about Mum being concerned, yada yada yada. He'd always had a tendency to disappear into his books, the way Sherlock engaged in sketchy deals and questionable missions, zipping off on his motorbike and returning with a check for 200 pounds. Fifty percent of which inevitably went into cigarettes and booze.

No, Khan was the good guy to his twin brother's badass, for the most part. Quiet and reserved, though his strong sense of justice resulted in furious outbursts sometimes.

"Is anyone sitting here?"

He glanced up, disconcerted. It was nearly midnight; why anyone else in their right mind would be spending Friday evening at the library was beyond him. This girl was pretty, if quite short, and despite the shyness with which she asked her question, the smile she flashed him was warm and confident.

"Sorry to disturb you," she added.

"Nobody's occupying this seat," Khan replied.

"Thanks." She extracted a MacBook Pro and began typing rapidly, the way Sherlock did when he was hacking computer systems as a recreational pastime. This initially aroused Khan's suspicion until he peered over her shoulder and saw, to his relief, a regular Word document.

"You type fast," he commented half an hour later. She didn't reply, engrossed in whatever she was doing. "What are you writing?"

"Stories," she answered shortly.

"What kind of stories?"

"Er... fiction."

"Mm. That's enlightening."

She grinned. "Sorry, I'm kind of on a roll here."

He tossed his pen and notebook onto the table and groaned. "And I, for one, am not."

She paused, fingers hovering over the keyboard. "What are you doing?"

"Problem," he muttered.

"That's equally enlightening," she retorted.

"Fair. I take a shitload of physics courses and they're killing me a little right now."

The girl wrinkled up her nose. "My utmost sympathy. Physics was the only class that legitimately made me cry in high school."

"Hated it that much?"

"I can't even begin to describe the horrors."

"Why didn't you withdraw then?"

"I had a crush on the teacher. That, and the fact that I'm an overachieving nerd who's too stubborn to give up on much."

"Ah."

"So what's all this?" She gestured to the pile of papers and angrily scratched out notes.

"Time travel."

She raised an eyebrow. "Time travel. In the flesh."

"Exactly." He yawned and ran a hand over his face. "My group and I are trying to prove that it's possible. I take it you're a skeptic?"

"I don't _not_ believe it exists. I just think it's a little silly to spend so much time researching something that might not even be possible. And anyway, if it exists, it exists, why the fuss?"

He looked blankly at her. "The _fuss_ is that time travel would enable so many people to do so many important things. Think of the genocides that could be prevented."

The girl shrugged. "Touche. I guess I feel like time isn't something to be messed with, since its nature is to move on, right? Why dwell on the past?"

"The genocide thing, primarily."

She nodded slowly. "You're passionate about these topics. I like it."

He felt himself start to blush, which was absurd, because he never really cared for compliments or insults. Indifference was a trait he and Sherlock had always shared. "Thanks."

"I'm the same, you know. Only about social issues. I can be a bit mule-headed when it comes to personal opinions, fair warning."

"Fair warning" implied that they would have further conversations, a prospect to which he had no objection. "I'm Khan, by the way," he said.

She smiled. "Edye."

"Nice to meet you."

"You too. And now, unfortunately, I'd better get going. My roommate's got a nasty habit of sneaking around at night, getting into all sorts of trouble, and we have exams this week so I'd prefer her not hungover or beaten up."

Khan gave a short laugh. "Ha. Sounds like my brother."

"They'd get along splendidly, then."

He tried to imagine Sherlock associating with a girl, and failed. "Mmhm," he said, and "see you around," as she packed her things up, zipped her jacket, and waved goodbye.

It didn't occur to him until he'd finally figured out some black hole business that he should have gotten her number.

—

Sherlock blinked at Khan from across the table. "What?" he asked impatiently.

"I didn't choose to do this, you know. Mum insisted. Apparently we don't talk enough."

"I'm done." Sherlock moved to stand up, his coffee and danish untouched. "I should get back to work."

"Come on, Sherly. Stay."

"Call me Sherly again and I will not hesitate to headbutt you."

"Fine. Sherl. No 'y'." He paused. No headbutting occurred: a positive sign. "Mum's got a point, you know. I talk to Mycroft more than I do you, and we live three blocks away from each other."

Sherlock slid back into his seat with a surly pout. "I have a busy schedule."

"False. You cut class all the time to go smoke with random people."

"Excuse me? When have I ever done so?"

Khan quirked an eyebrow. "Yesterday afternoon, perhaps? A dark-haired young lady bummed you a smoke."

Sherlock didn't need to ask. "Mycroft."

"Yup."

"God, will he ever stop stalking me?"

"He cares about you."

"I'm fine," Sherlock snapped.

"Are you, though?" Silence. Then,

"For the record, I was working, and I was on break. I don't skip an excessive amount of classes, only the ones for which I have no patience."

"As in, all of them."

"We have equally brilliant minds, Khan. You're just more tolerant."

"Valid. I still think you should try to stick with it."

"Everybody's so dull and uninteresting nowadays," Sherlock complained. "I appreciate that no one's going to have the deduction abilities I do, but they could at least be fucking _real_."

Khan steepled his fingers beneath his chin, tilted his head in a question. "What do you mean?"

"Every single person who walks into this shop is the same. Fake smiles, fake interest, and half the girls try to flirt with me simply because I am, from an objective point of view, attractive."

"Thanks." Khan smirked; they were virtually identical, aside from the fact that Khan slicked back his hair, while Sherlock's let his curls stay rampant and unkempt. A compliment to his brother's appearance was automatically one to his.

"Don't patronize me."

"I'm not!"

"_Anyway._ I'm fed up, Khan. Doesn't it get exhausting for you, having all this knowledge and potential and then having to deal with saccharine, artificial personalities and insincere flattery?"

"It's not exhausting because I have an outlet for all that knowledge and potential."

"Your science time travel shit."

"You mean physics."

"No, I'm fairly certain I mean 'science time travel shit.'"

He was a lost cause. Khan threw in the towel. "I'm just saying, you might want to consider the possibility of channeling all your energy into productive things, rather than smoking and alcohol and breaking into government systems. Illegal, by the way. Can't stress that enough."

Sherlock cast him a dubious look. "Maybe."

"Think about it," said Khan firmly. "Now go back to work."

Sherlock trudged off towards the counter.

"Wait!" called Khan.

"What?"

"Who was the girl?"

Sherlock paused, turned around. Something in his demeanor shifted. "Leila," he said simply, and returned to his post at the register.


	2. Chapter 2

Leila was still wide awake when Edye returned. "Good study session?"

Her roommate made a face. "I may have just written fanfiction the entire time."

"Edye!"

"At least I met a guy. He was kind of cute."

"And you accuse me of not taking care of myself."

"Speaking of, you should really go to bed."

"Why sleep when there's so much thinking to be done?"

"Because," said Edye patiently; they'd had this argument all too many times, "sleep is good for your brain. And it keeps you stable. It's just as important as food, you know."

"Yeah, okay."

"You're not fooling me."

"I wasn't trying to."

Edye poured tea into her white Starbucks tumbler and shrugged. "It's your life. Goodnight." She screwed the cap on, grabbed her bag, and retreated to her room.

"You're lovely!" Leila called. "You really are!" Edye gave a mollified "sure" from the hall, and, needless to say, Leila did not go to sleep.

—

Sherlock gave the countertop a final lazy spray of cleaning solution, swiped a rag over its surface, and tossed it carelessly over his shoulder. "See you tomorrow," he said to Mrs. Hudson, who waved at him. He snatched his keys from the back room and headed out back where, whistling, he revved the engine on his motorbike.

"Don't run me over, please," said a voice. He was not one to forget voices easily.

"Leila."

"Yeah. Sherlock, right?"

His name was a distinctive, generally unforgettable one, and the fact that she hadn't cared enough to commit it to memory was both irritating and intriguing. "My apologies. Please do proceed."

She crossed the driveway in front of him, lingered there for a moment. Shadows cast across her face accentuated bold features and thick hair. "You didn't really get in trouble or anything, did you, for smoking?"

"No, I do it all the time. My brother may have an unfortunate habit, however, of surveilling my activity. He relayed his observations to my twin brother, who did not hesitate to broach the subject with me."

"You have a twin brother?"

"Indeed. Don't worry, he's not at all like me. The only thing we have in common, really, is our intelligence. He uses his – for lack of a more sophisticated word – brain power to study time travel, whereas my drug of choice, so to speak, is... well, drugs. Smoking. Alcohol. Sketchy deals. The like."

"I don't know, those sound pretty damn exciting to me. I have a somewhat similar lifestyle, though my roommate is perpetually trying to rein me in."

"Same with my brothers." Again, the silence was oddly comfortable. Almost made him wish he knew more about interpersonal relations. "Well," he finally said. "I'll see you around."

"Good luck with your sketchy deals," she replied, and left without further ado.

—

Edye went to the library after an exhilarating lunch with one of her favorite professors. Dr. Guiney taught a handful of biology courses; she and Edye had developed a close relationship from day one. In addition to bio, Edye was an avid writer (creative and, for the most part, fanfiction), and also working at an education degree.

She went to her usual spot, which happened to be the table at which she'd met Khan. "Hey," she said, sliding in next to Madeline, a long-time pal from grade school. "How've you been?"

"Alright," Madeline replied distractedly. "Studying, mainly."

Edye knew better than to disturb her studious friend further, and plugged in her laptop. They worked side by side quietly, every so often asking for advice on paragraph structure or what transition word worked where, and Edye was just about to take a break and run some errands when Khan materialized.

"Hi," he said. "Anybody sitting here?"

"No," she replied, pleasantly surprised. "Khan, right?"

He nodded. "Edye."

Madeline waggled her eyebrows suggestively at her friend, who kicked her under the table. "How's the time travel going?" Edye asked.

"Pretty well, actually," he said. "The other day –"

"Well, I have to go," said Madeline loudly, making a show of gathering her things. "Bye, Edith."

Edye wrinkled up her nose and waved, then turned back to Khan. "Sorry, come again?"

"I thought your name was Edye?"

"What? Oh, that. My technical, legal name is Edith, but nobody's ever called me that, so naturally when Madeline discovered my true identity, she began using 'Edith' as a 'nickname.' Ironic, I know. I have a weird name, nobody can spell it or figure out how to pronounce it." She was babbling, and she knew it. Christ. Did Khan really have to be so goddamn attractive?

Thankfully, he took the tangent in stride, and said sympathetically, "Tell me about it. My family's the prime example of strange names. Compared to my brothers, I've got an utterly commonplace one."

"Really? What are their names?"

Khan smirked. "Sherlock and Mycroft."

"Ouch. Bet they got teased a lot in school."

"Mycroft is too high-and-mighty to elicit anything more than fear, but Sherlock bore the brunt of it all. Given that we're twins, we were constantly compared – still are, in some situations – and my name was relatively more normal than his, so."

"You have a twin brother? No way! What's he like? Are you identical?"

"We are identical. Physically. Not personality-wise. He's the one I mentioned before, the one similar to your roommate?"

"Oh. Yeah, Leila's a little –"

"Hold up. Her name's Leila?"

"Um, yes. Why?"

"No reason."

Awkward silence prevailed. This felt like an excellent time to make an escape, but she did not want to leave, not least because her only alternative was returning to the flat, and she had no desire to run into a sleep-deprived Leila expounding upon deep life philosophies that seemed inappropriate to daylight. Khan appeared deep in thought, so she asked tentatively, "Physics problem suddenly come up?"

"What? No. I just... Sherlock was saying..." He shook his head. "Never mind. Common name, Leila, isn't it?"

What was happening? "I suppose so."

"Sorry, sorry. Anyway. I presume you were about to leave?"

Startled, Edye replied in the affirmative. "How did you know?"

"Your hand's still in the loop of your bag, and your charger's unplugged, indicating that you were preparing to go elsewhere. Probably errands; your wallet's on the table. Rudimentary deductions."

Her eyes widened. "That's really cool."

"I'm nothing compared to my brother. He's gotten punched more than once. Also kicked out of parties – parties filled with science nerds, mind you – for scaring off potential guests."

"I'm sure you're something," said Edye, hoisting her backpack onto the table and zipping up the laptop sleeve. "You know. Compared to your brother."

Khan appeared not to know what to say, and, feeling very embarrassed, Edye grabbed her keys and all but speed-walked out of the library, at which point she completely forgot where her car was and wandered around aimlessly for the next half hour. Despite the fact that they'd only spoken twice, Khan was beginning to be a real problem.

—

The bloody construction workers were relentless. After shutting all the windows, blasting music into noise-cancelling headphones, opening the windows, hollering some profanities at them, and calling Edye to no avail, Leila stormed out of the flat, heading for the center of town. Their incessant drilling and pounding and hammering had given her a headache, and she quite fancied a cig.

Bringing her wallet might have been a good idea too.

Swearing under her breath, she left the corner store and found a park bench not occupied by a homeless man, where she sat and contemplated the current state of her life. For the middle of freshman year, it wasn't too bad. Edye'd been struggling lately, though, which honestly put her in a horrible mood sometimes. Watching someone who was so obviously competent in nearly every aspect of their life beat themselves up for no reason was maddening and pointless, in her opinion.

"You look like you could use this." A cigarette was pressed into her palm, followed by a pair of skinny legs as Sherlock climbed over the back and sat down next to Leila.

"How'd you know?" She braced herself for an onslaught of observations.

He leaned back, feet angled outward, and said simply, "The expression on your face. Your posture. And the fact that you're extremely sleep deprived, so I assume your cravings are keeping you up at night."

"Sleeping is dull," she said, careful to maintain a bored facade.

"I agree."

She didn't have anything particularly pressing to say, and neither, it seemed, did he. Though it would not be overly unusual for her to befriend what Edye dubbed "unsavory characters," she had fallen into a strangely comfortable routine with Sherlock, especially considering that she'd only encountered him three times. He was so unlike most of the boring blokes with whom she'd associated in the past: he felt no present need to fill silences, and she got the sense that he appreciated her acceptance of his idiosyncrasies. Either way, it was nice.

"How's your psychology course?" he asked suddenly.

"Fine," she answered. "How...?"

"Psychology textbook," he said. "Painfully obvious, that."

Sticking out of her backpack in plain sight. Of course. "Got it. It's going alright."

"Should you be in class right now?" He eyed her keenly over his long nose.

"As a matter of fact, no. Not for another half hour."

"You aren't planning on attending."

"Well, now I am."

A vague smile flitted over his lips. He had quite a lovely mouth. "Contrary, are we? People will take advantage of that."

She shrugged. "I enjoy proving myself."

"You like psychology. Why don't you go to the lectures?"

"They're boring and don't tell me anything I don't already know."

"And you know everything there is to know?" There was no trace of sarcasm; he was genuinely curious. She was slightly flattered at the lack of doubt.

"No, but enough to pass the class without going to it."

"Precisely my attitude all throughout high school."

"It's a good attitude. I approve."

"Excellent."

She stamped out the cigarette, then stood up. "Thanks for the smoke. I've got to go attend a lecture now."

"You aren't going to stay the entire time. Or take notes. Your handwriting's abominable," he added.

Not bothering to question the handwriting comment, she insisted, "I'm going to stay. Particularly given that challenge."

"Again, people can really take advantage of that. Be careful."

She started walking away. "I'm serious."

"I'll need proof!" he called. "Text me. I expect a full page of notes."

"You don't have my number," she tossed back, turning around to smirk at him.

He waved a hand dismissively. "Next time," he said, and Leila, grinning, went to class.

—

"It's midnight."

Leila didn't take her eyes off the computer screen. "Yup."

"I don't suppose bedtime is happening anytime soon."

"Nope."

Edye sighed and tugged her hair back into a ponytail. "Well, I'm exhausted."

"Night."

"Aren't you going to ask about my day?"

"Sorry. How was your day?"

"Good. I ran into Cute Library Guy again."

"How did that go?"

"I panicked and fled, then got lost in the town I grew up in."

"So, typical."

Edye chuckled. "Precisely."

"Are you going to ask him out?"

"I've seen him twice."

"You clearly like him."

"He probably doesn't like me." Edye eyed her reflection critically in the television behind Leila's head. "Why would he, though? I'm not, like, pretty or smart or –"

"I don't want to hear it," Leila said sharply. "You're fine. Now stop it."

"I'm not –"

Leila snapped her laptop shut and folded her hands on the table. "Edye. You are being unnecessarily hard on yourself, as always, and it needs to stop."

"You don't –"

"I don't see the point in this," Leila said in frustration. "And I'm sorry, I'm not going to sugar coat it and tell you that you're perfect and it will be okay because you should fucking _know_ that already!"

"You don't need to be cynical," Edye said, looking hurt.

"Oh, please. We both know I'm the definition of 'cynical.' I don't believe in happiness, I'm virtually incapable of caring, and –"

"Fine," said Edye shortly, wrapping her arms protectively around herself. "Thanks for that." She flounced off to bed, leaving Leila sitting in semi darkness and feeling intensely annoyed. What was wrong with people nowadays? She literally saw no purpose in all this worrying; it would be one thing if her roommate was ugly and stupid, but she clearly wasn't, so why in god's name was she wasting so much time fretting about it?

Heaving a sigh, Leila snatched up her coat and left.


End file.
